A classification system (10) having a controller (12), a document storage memory (14), and a document input (16) is used to classify documents (20). The controller (12) is programmed to generate a theme score from a plurality of source documents in a plurality of predefined source documents. A theme score is also generated for the unclassified document. The unclassified document theme score and the theme scores for the various classes are compared and the unclassified document is classified into the classification having the nearest theme score.